How to set default text inset for all Keynote shapes?

On the Keynote format panel, the text panel has "Layout" control with "Text Inset" specified as 3 by default.

I changed it in my "Set as default textbook appearance" but in shapes etc., which I frequently modify with text, it still defaults to 3.

Is there a method to set that for EVERY instance of text? Maybe in a new theme?

[Re-Titled by Moderator]

Original Title: Modify text inset default?